Well.....I did my search (on a quite fantastic page
http://www.lerc.nasa.gov/WWW/K-12/airplane/short.html ) and found out, very quickly, about magnus effect (already understood coanda).
Question now is that these two topics where on a list of questions that were, supposedly, about the PA28.
Cannot think of anything that produces coanda on the a/c (other than, as said earlier, something to do with airflow above and below an aerofoil...but that screws up my separation point ideals).
Only thing I can think of which could produce magnus effect is the rotation of the wheels and tyres immediately after rotation - producing, I suppose, a very small downward "force" (opposing lift?? ????)
Anybody got any ideas??